Integral-resonant voltage control for three-phase four-leg voltage source inverters

This paper deals with a newly-conceived voltage control method for three-phase four-leg voltage source inverters (VSI) which are being required in autonomous power generating units devoted to supply both three-phase and single-phase electrical loads in four-wire electric power distribution systems. In order to deal with VSI operating conditions providing three-phase voltage supply of both unbalanced loads and non-linear loads, an Integral + Resonant (I+R) voltage control structure is discussed and experimentally verified by means of a 25 kVA rated power converter prototype. It is shown that the proposed voltage control allows simplifying the overall control configuration, achieving zero-overhead power factor regulation and fast compensation of load unbalances. Further to that, a complete current limiting strategy is described and tested under different load conditions.